You can render your model as you want it to be seen, goto the model edit page, upload the image and then set the image as the default image. Alternatively you could try re-arranging the orientation of the model before uploading - iirc, Y is the 'vertical' axis, and Z the 'depth' axis.

For oddness 's sake, if you scale your model by 10, you can regard a blender unit as centimeter, if you scale it by 25.4, you can regard a blender unit as an inch, You can properly scale the model in the N panel, by setting a bounding box dimension, then copying the scale in that dimension to the other scale dimensions values in that panel . It sounds odd, but experiment with a STL export to NetFabb to see proof.

Have any questions regarding Blender, and need fast answers, you are always welcome at the IRC Server Freenode, channel #blender. As a bonus, several there have experience in modelling for 3D prints.